Description

The getservbyname(), getservbyport() and getservent() functions each return a pointer to a
servent structure, the members of which contain the fields of an entry
in the network services database.

The getservent() function reads the next entry of the database, opening a
connection to the database if necessary.

The getservbyname() function searches the database from the beginning and finds the
first entry for which the service name specified by name matches the
s_name member and the protocol name specified by proto matches the s_proto member,
opening a connection to the database if necessary. If proto is
a null pointer, any value of the s_proto member will be matched.

The getservbyport() function searches the database from the beginning and finds the
first entry for which the port specified by port matches the s_port
member and the protocol name specified by proto matches the s_proto member, opening
a connection to the database if necessary. If proto is a
null pointer, any value of the s_proto member will be matched.
The port argument must be in network byte order.

The setservent() function opens a connection to the database, and sets the
next entry to the first entry. If the stayopen argument is
non-zero, the net database will not be closed after each call to
the getservent() function, either directly, or indirectly through one of the other getserv*()
functions.

The endservent() function closes the database.

Usage

The port argument of getservbyport() need not be compatible with the port
values of all address families.

The getservent(), getservbyname() and getservbyport() functions may return pointers to static data,
which may be overwritten by subsequent calls to any of these functions.

These functions are generally used with the Internet address family.

Return Values

On successful completion, getservbyname(), getservbyport() and getservent() return a pointer to a
servent structure if the requested entry was found, and a null pointer
if the end of the database was reached or the requested entry was
not found. Otherwise, a null pointer is returned.